US20120000353A1

US20120000353A1 - Pilot-operated directional control valve, particularly for controlling an actuating cylinder of a turbo-machine

Info

Publication number: US20120000353A1
Application number: US12/741,899
Authority: US
Inventors: Steffen Lindoerfer; Lothar Ochs
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2007-11-09
Filing date: 2008-09-16
Publication date: 2012-01-05
Also published as: EP2209998B1; DE102007053877B3; CN101855458B; WO2009059658A1; EP2209998A1; CN101855458A; JP2011503453A; US8555772B2

Abstract

A directional control valve for controlling working cylinders, servomotors, or an actuating cylinder of a turbo-machine such as gas and steam turbines, the directional control valve includes a force-regulated magnet and a hydraulic unit. The hydraulic unit includes a pilot piston and a control housing in which the pilot piston is situated so it is displaceable in an axial direction of the directional control valve. The control housing has at least three hydraulic connections including a first pressure connection configured for connection to a hydraulic pressure supply, at least one consumer connection configured for connection to the working cylinder or the servomotor, and a tank connection configured for connection to a hydraulic tank. A flow cross-section between the hydraulic connections being variable by displacement of the pilot piston. The valve also having an actuating unit that includes a control piston, an actuating piston, a first elastic element, a second elastic element and a conductor. The control piston is displaceably located in the control housing or in a flange attached on the control housing. The control piston is displaceable using the force-regulated magnet, the control piston being configured to vary the flow cross-section between an actuating unit pressure connection, an actuating piston connection and an actuating tank connection by displacement. The actuating piston is non-positively and/or positively connected on the pilot piston such that the actuating piston is displaceable in the axial direction of the directional control valve. The actuation piston divides a piston room into a first piston room chamber and a second piston room chamber, the chambers being sealed from one another. The first piston room chamber is hydraulically connected to the actuating piston connection. The first elastic element acts against a hydraulic pressure force in the first piston room chamber. The actuating piston being connected by way of the first elastic element to the control piston or being supported thereon. The second elastic element acts against the hydraulic pressure force in the first piston room chamber. The actuating piston being connected by the second elastic element to the control housing or the flange or being supported thereon. The conductor is situated in a magnetic field of the force-regulated magnet. The force-regulated magnet being an electromagnet configured for electrical activation. The conductor is electrically connected to the electromagnet and a control unit for control of the electromagnet such that the magnetic force and the position of the control piston, the actuating piston, and the pilot piston are regulated by way of a Hall voltage generated in the conductor.

Description

The present invention relates to a directional control valve for controlling working cylinders or servomotors, in particular for controlling an actuating cylinder of a turbo-machine, such as a gas or steam turbine, a control piston (pilot piston) of the directional control valve being displaced using a force-regulated magnet and thus varying the flow cross-section between hydraulic connections and/or alternately producing connections between various connection pairs.
The use of directional control valves for the control and/or position regulation of working cylinders is known. For single-acting cylinders, for example, 3/3 directional control valves having spring return are used and 4/3 directional control valves having spring return are used for double-acting cylinders. These each have a control piston, which is actuated via an electromagnet. The electromagnet presses the control piston against a spring and thus connects a pressure connection P to a consumer connection and/or one of two consumer connections A, B, in order to conduct pressurized hydraulic medium via the particular connection into a predetermined chamber of the consumer. For example, in the case of double-acting working cylinders, the consumer connection A is connected to a first cylinder chamber of the working cylinder, and the consumer connection B is connected to a second cylinder chamber, which is separated by a cylinder piston from the first cylinder chamber. Depending on which of the cylinder chambers pressurized hydraulic medium is to be introduced into from a hydraulic pressure supply via a directional control valve, a piston rod attached to the piston of the working cylinder is retracted or extended.
In such double-acting cylinders, the 4/3 directional control valve is typically implemented in such a manner that whenever the first consumer connection A and thus the first cylinder chamber of the working cylinder is connected to the pressure connection P, the second consumer connection B and thus the second cylinder chamber of the working cylinder is connected to a tank connection T of the directional control valve or vice versa. The tank connection T is distinguished by a comparatively low hydraulic pressure, so that hydraulic medium slides out of the cylinder chamber connected to the tank connection T and is guided to a hydraulic tank.
Depending on whether and how far the control piston of the directional control valve is displaced using the electromagnet against the pressure force of the restoring spring, either the first consumer connection A is connected to the pressure connection P or the second consumer connection B is connected to the pressure connection P and the particular other consumer connection is connected to the tank connection T. Hydraulic medium thus either flows to one or the other side of the piston of the working cylinder and the retraction or extension of the piston and/or a piston rod of the working cylinder, which is attached to the piston, is controlled.
In order to position the piston with its rod at a position, a closed control circuit is required. For this purpose, a position measuring device, also referred to as a position encoder, is provided on the working cylinder, whose measuring signal is returned to control electronics integrated in the electromagnet of the directional control valve. These control electronics compare the measured value to the target value and calculate a new manipulated variable for the magnet from the difference. The force of the magnet then accordingly increases or decreases and displaces the control piston in the required direction in order to correct the location of the piston of the working cylinder. The control piston of the directional control valve is non-positively connected to the magnet armature of the electromagnet, i.e., the part of the magnet which is retracted or extended from the magnet by varying the control voltage or the control current strength, and the adjustment movement of the control piston is performed directly by the magnet armature, i.e., both components—magnet armature and control piston—always move jointly in the displacement direction of the control piston.
The flow cross-section between the consumer connection A, B and the pressure connection P and/or the tank connection T is determined by a ring gap, which the control piston delimits with a control housing, in which it is situated so it is displaceable in the axial direction. Because the stroke of the electromagnet is limited, the flow cross-sections which a typical directional control valve can open and close are limited. The diameter of the control piston also cannot be enlarged arbitrarily in order to thus expand the flow cross-sections, because its mass thus increases and it could no longer be exactly dynamically positioned in connection with a spring in the closed control circuit by the magnet. In particular, the occurring mass forces, natural frequencies, friction forces, and oscillations are to be viewed as problematic.
To be able to use directional control valves for controlling actuating cylinders of turbo-machines in spite of the described problems, having a larger control piston diameter for enlarging the flow cross-sections in the directional control valves, on the one hand, there is the possibility of implementing the electromagnets used as larger and stronger. However, this would also result in higher inductances and larger armature masses, which would have disadvantageous effects on the dynamic response, the required installation space, and the costs of the directional control valve.
In another design, additional position measuring devices and/or position encoders are provided, using which the position of the control piston is measured, and the measuring signal is returned to the control electronics of the electromagnet. An enlargement of the magnet is not necessary in these embodiments. However, the sensitivity of the position encoder with respect to temperature and oscillation influences is disadvantageous. In particular in the case of the use of such a directional control valve for controlling and/or regulating an actuating cylinder of steam turbines or gas turbines, the high ambient temperatures of the position encoder, which are caused by the medium of gas or steam, which is to be varied with respect to its flow quantity, result in short maintenance intervals and possibly a comparatively early breakdown of the directional control valve.
The present invention is based on the object of disclosing a directional control valve which is improved with respect to the known embodiments. In particular, the directional control valve according to the invention is to be able to position the piston rod of a comparatively large working cylinder (single-acting or double-acting) rapidly and exactly and to control the accordingly required large flow quantities precisely and reliably by the directional control valve. Finally, the directional control valve is to be producible cost-effectively and is to have a long lifetime.
The object according to the invention is achieved by a directional control valve having the features of claim 1. The dependent claims describe particularly advantageous embodiments of the invention.
A directional control valve according to the invention for controlling working cylinders, servomotors, or the like, in particular for controlling an actuating cylinder of a turbo-machine, such as a gas or steam turbine, has, in addition to a force-regulated magnet, typically an electromagnet, a hydraulic unit, which comprises a control housing, in which a control piston—referred to as a pilot piston in the present case—is situated so it is displaceable in the axial direction of the directional control valve. The control housing has at least three hydraulic connections, for example, precisely three hydraulic connections, in order to implement a 3/3 directional control valve, or four hydraulic connections, in order to implement a 4/3 directional control valve, namely a pressure connection P, a consumer connection A and/or B, and a tank connection T. The pressure connection P is intended for connection to a hydraulic pressure supply and the tank connection T is intended for connection to a hydraulic tank. The consumer connection(s) A, B is/are intended for connection to a consumer, the working cylinder or the servomotor here.
The flow cross-section between the hydraulic connections A, B, P, T is varied by displacing the pilot piston, as was described in the introduction to the description. However, an additional actuating unit is provided according to the invention for the hydraulic unit, which comprises, on the one hand, the force-regulated magnet and an additional control piston, which is situated so it is displaceable in the control housing or in a flange attached to the control housing. The term flange refers to any suitable structural form of an additional housing or a receptacle device, which can be implemented integrally with the control housing or can be attached thereto, typically non-positively and positively. The control piston is associated with the force-regulated magnet in such a manner, in particular supported on a magnet armature thereof or connected non-positively and/or positively thereto, that the control piston is displaced by the force-regulated magnet as a function of the activation of the magnet. The activation of the magnet, which is implemented as an electromagnet, using a greater voltage or a greater current strength will typically extend the magnet armature further, in particular against the force of an elastic element, such as a compression spring, and thus press the control piston in a direction away from the magnet. In the case of a lower control voltage or a lower current strength, the magnet armature retracts correspondingly, in particular due to the force of the elastic element or the compression spring.
The additional actuating unit has an actuating unit pressure connection p, an actuating unit tank connection t, and an actuating piston connection a. The actuating unit pressure connection p can particularly be connected to a separate pressure supply, which is separated with respect to the pressure connection P and/or the pressure supply of the control housing, and is thus protected from pressure drops due to possible large volume flows through the hydraulic unit.
The actuating unit tank connection t can be connected to the hydraulic tank which is associated with the hydraulic unit or to an additional hydraulic tank.
The actuating unit also has an actuating piston according to the invention, which is also displaceable in a piston room in the axial direction of the directional control valve, i.e., in the same direction as the pilot piston of the hydraulic unit, and is non-positively and/or positively connected to the pilot piston. The actuating piston divides the piston room into two piston room chambers, which are sealed off from one another, so that a higher or lower pressure can be set in the first piston room chamber than in the second piston room chamber. The first piston room chamber is hydraulically connected to the actuating piston connection a, for example, via holes, in particular holes in the axial direction in a housing or cylinder, in which the actuating piston is supported so it is displaceable. The second piston room chamber can be continuously hydraulically connected to the actuating unit tank connection t, for example, but could also be air filled and/or connected to the surroundings of the directional control valve. Other connections are possible.
The actuating piston is further connected via a first elastic element, in particular a compression spring, referred to in the present case as a measuring spring, which acts against the hydraulic pressure force in the first piston room chamber, to the control piston, in particular positively and/or non-positively, or at least supported thereon, and connected via a second elastic element, which also acts against the hydraulic pressure force in the first piston room chamber, for example, also in the form of a compression spring—referred to in the present case as a restoring spring—to the control housing or the flange, again advantageously positively and/or non-positively, or is at least supported on one of the two. The measuring spring can thus cause the above-described retraction of the magnet armature at comparatively low voltages and/or current strengths of the electromagnet.
The first elastic element, in particular the measuring spring, advantageously has a different spring force than the second elastic element, in particular the restoring spring. The first elastic element—measuring spring—will typically have a lesser spring force than the second elastic element—restoring spring.
If compression springs are provided as the elastic elements, they are typically situated in the second piston room chamber. Of course, it is also possible to provide one or more tension springs instead of compression springs, in particular instead of the restoring spring, which is/are then advantageously situated in the first piston room chamber or outside the piston room chamber.
The measuring spring is advantageously implemented having a smaller external diameter than the restoring spring and can thus be positioned radially inside the restoring spring in a space-saving manner. The restoring spring encloses the measuring spring in the peripheral direction. Both springs may have approximately the same axial length and/or essentially the same turn count.
An actuator according to the invention, which comprises a working cylinder, in particular in the form of an actuating cylinder of a turbo-machine, also has a directional control valve of the described type, which is connected via hydraulic lines to the working cylinder for controlling or regulating the position of the retractable and extendable piston and/or the piston rod of the working cylinder. As known, a position measuring device can be connected to the working cylinder, which detects the position and/or the covered distance of the piston and/or the piston rod of the working cylinder and is connected to a control unit, in particular integrated in the force-regulated magnet, in order to regulate the actuation of the control piston and thus the actuating piston and pilot piston via the magnet as a function of the measurement results. The directional control valve itself can be free of any measuring device, which measures the movement or the position of one of the pistons or components connected thereto.

The invention is to be described for exemplary purposes hereafter on the basis of an exemplary embodiment. In the figures:

FIG. 1 shows a possible embodiment of a directional control valve implemented according to the invention;

FIG. 2 shows a detail of the additional control unit, which is shown enlarged from FIG. 1.

The hydraulic unit may be seen in FIG. 1, which is formed by the control housing 2 having the pilot piston 3, which is displaceable therein in the axial direction. The control housing 2 has four hydraulic connections, namely a pressure connection P, a first consumer connection A, a second consumer connection B, and a tank connection T. The connections are connected as described at the beginning to a hydraulic pressure supply, the two cylinder chambers of the working cylinder, and a hydraulic tank.
The pilot piston 3 has a comparatively large diameter, and the comparatively large cross-section of the various hydraulic connections A, B, P, T, of which the pressure connection P and the two consumer connections A, B are connected to annular chambers in the control housing 2, allow large volume flows through the directional control valve. The listed three annular chambers, which are formed and/or delimited by the control housing 2 together with the pilot piston 3, may be the only annular chambers of the hydraulic unit and/or the control housing 2. The pilot piston 3 has holes or slots running in the radial direction, which allow an outflow of hydraulic medium from the first consumer connection A and/or the second consumer connection B to the tank connection T as a function of the axial position of the piston 3 in the control housing 2, in that they have flow-conducting connections thereto, the tank connection T being implemented on a frontal end of the directional control valve in the axial direction thereof in the embodiment shown.
The radial holes or radial slots in the pilot piston 3 thus allow the conduction of hydraulic medium into the interior of the pilot piston 3 and from there to the tank connection T.
The directional control valve is driven by a separate actuating unit 1, which comprises a 3/3 way valve having single-acting actuating piston 1.5, which is situated axially thereto, having spring return. The 3/3 way valve is formed by a control piston 1.1, which is situated so it is displaceable—also in the axial direction of the directional control valve here—within a flange 1.2 and implements an actuating unit pressure connection p, an actuating piston connection a, and an actuating unit tank connection t with the flange 1.2, see FIG. 2 in particular. The actuating unit pressure connection p is connected to a separate pressure supply and is thus protected from pressure drops due to large volume flows in the hydraulic unit.
The control piston 1.1, which is directly connected to the magnet armature of the force-regulated magnet 1.9, is received in a central cylindrical hole of the flange 1.2. Two annular notches are incorporated in the hole, which form a first chamber together with the control piston 1.1, which is hydraulically connected to the actuating unit pressure connection p and in which the hydraulic pressure of the pressure connection thus prevails, and form a second chamber, which is connected to conduct hydraulic medium to the actuating piston connection a.
The flow connection between the annular chamber connected to the actuating piston connection a and the actuating unit tank connection t is produced via radial holes in the control piston 1.1. From there, the hydraulic medium flows further into an installation room of two compression springs—measuring spring 1.4 and restoring spring 1.6—which apply pressure to an actuating piston 1.5, which is described in greater detail hereafter, and finally back in the flange 1.2 to the actuating unit tank connection t. The actuating unit pressure connection p can be connected in the same axial plane of the flange 1.2.
A cylinder 1.7 is inserted in the flange 1.2—and also in the control housing 2 in the present case—in which the actuating piston 1.5 is situated so it is displaceable in the axial direction of the directional control valve and is friction-sealed in relation to the inner surface of the cylinder 1.7, for example, via a seal or a guiding band. The actuating piston 1.5 divides a piston room 1.10, which is delimited by the cylinder 1.7 in the peripheral direction and at one axial end and is delimited at the opposing axial end by the flange 1.2, into a first piston room chamber 1.11 and a second piston room chamber 1.12. The first piston room chamber 1.11 is connected to conduct hydraulic medium via holes 1.13, which are introduced in the axial direction into the wall of the cylinder 1.7, to the actuating piston connection a. The second piston room chamber 1.12 forms the installation room, which is connected to the actuating unit tank connection t, for the measuring spring 1.4 and the restoring spring 1.6.
The restoring spring 1.6 is clamped between the flange 1.2 and the actuating piston 1.5. The measuring spring 1.4 has a smaller diameter than the restoring spring 1.6 and can therefore be situated in a space-saving manner in the interior of the restoring spring 1.6. Its first axial end is supported via the rod 1.3 on the control piston 1.1 and its other, opposing end is also supported on the actuating piston 1.5. The measuring spring 1.4 pushes the control piston 1.1 in the direction of the magnet 1.9 against a locking ring in the idle position and thus always holds the composite of measuring spring 1.4, rod 1.3, and control piston 1.1 centrally and in a defined manner on the stop.
The coupling of the actuating unit 1 and/or the actuating piston 1.5 to the pilot piston 3 of the “large directional control valve” (the hydraulic unit) is performed non-positively and positively. The narrow end of the actuating piston 1.5 is fitted in a pilot piston floor, in the form of a disk 4 here, and is screwed thereon using multiple hex nuts. Of course, other connections also come into consideration. For this purpose, the narrow end of the actuating piston 1.5, which can also be referred to as a piston rod, extends through the cylinder cover 1.8, which is screwed frontally onto the cylinder 1.7 in the embodiment shown and forms the described axial delimitation of the piston chamber 1.10 and/or the first piston room chamber 1.11. This piston rod is also guided through the cylinder cover 1.8 and is sealed with respect thereto, for example, using an inserted sealing ring.
For example, the magnet 1.9 is screwed frontally on to the flange 1.2, as shown, and the tappet rod of its armature presses into the center of the control piston 1.1 and moves the control piston 1.1 in the direction of the actuating piston 1.5 and/or the pilot piston 3. The force-regulated magnet 1.9 advantageously comprises the control electronics for the pilot drive (actuating unit 1) and for a working cylinder (not shown) attached to the directional control valve, and is particularly interconnected with a position measuring device of the working cylinder, as described at the beginning. The control electronics can be implemented as analog or digital and can be adapted with respect to the controlled system to the size of the working cylinder to be controlled.
In the embodiment shown, the control piston 1.1, the actuating piston 1.5, and the pilot piston 3 are thus situated concentrically one behind another and aligned with one another in the axial direction. The flange 1.2, the cylinder 1.7, and the control housing 2 are also situated concentrically to the common longitudinal axis of the various pistons.
The control method executed according to the invention using the directional control valve shown will be described hereafter.
After predefining a position target value for the working cylinder (not shown) using a current, in particular between 4 and 20 milliamps, applied to the magnet 1.9, which is implemented as an electromagnet, the controller immediately experiences a control deviation. The control electronics calculate a magnetic force target value therefrom as the manipulated variable. The changing magnetic force has the result that the magnet armature is deflected and the control piston 1.1 presses to the right against the measuring spring 1.4. The 3/3 way valve opens, which is formed by the control piston 1.1 together with the flange 1.2, and releases the passage of the room connected to the actuating unit pressure connection p and the room connected to the actuating piston connection a. Armature and control piston 1.1 move in the direction of the actuating piston 1.5 and/or pilot piston 3 until the magnetic force and the measuring spring force are in equilibrium. A spring balance is thus formed. The actuating piston 1.5 moves because of the pressurization of the first piston room chamber 1.11 with the supply pressure via the connection of the two cited chamber (p to a) in the direction of the control piston 1.1 or away from the pilot piston 3 (the positive connection between these two pistons is still to be noted) and compresses the measuring spring 1.4 further, until it closes the passage or flow cross-section between the two chambers again, which are connected using the actuating unit pressure connection p and/or the actuating piston connection a, using its force and holds the system in equilibrium. This equilibrium state can also be referred to as the hydraulic center.
Because of the rigid attachment of the actuating piston 1.5 on the pilot piston 3, it also executes the movement of the actuating piston 1.5 and accordingly regulates the flow cross-section between the hydraulic connections A, B, P, and T of the control housing 2 of the hydraulic unit.
Vice versa, if a movement of the working cylinder piston (not shown) and, for this purpose, the pilot piston 3 is required in the other direction, the magnetic force is reduced, the control piston 1.1 moves in the direction away from the actuating piston 5 and/or the pilot piston 3, and toward the magnet 1.9, and releases the passage (flow cross-section) between the chamber connected to the actuating piston connection a and the actuating unit tank connection t. The hydraulic medium, in particular oil, is pressed out of the cylinder 1.7, namely the first piston room chamber 1.11, by expansion of the restoring spring 1.6. The actuating piston 1.5 moves in the direction away from the control piston 1.1 (to the right in the illustration shown) and relaxes the measuring spring 1.4. It relaxes precisely until the prevailing magnetic force presses the control piston 1.1 to the right and ends the outflow of the hydraulic medium from the first piston room chamber 1.11 via the actuating piston connection a and the actuating unit tank connection t to the hydraulic tank (not shown). The magnetic force and the measuring spring force are again in equilibrium.
The magnetic force change and the stroke change of the actuating piston 1.5 and thus of the pilot piston 3 are proportional to one another. A magnetic force change is therefore always associated with a unique position of the actuating piston 1.5 and thus the pilot piston 3.
An electrical conductor can be situated in the magnetic field of the force-regulated magnet 1.9 to measure the magnetic flux density via a Hall voltage induced in the conductor. This conductor (not shown) can be connected to the magnet 1.9 and/or the control electronics for the magnet 1.9 in such a manner that the magnetic force is regulated via a return of the Hall voltage. Therefore, the actuating piston 1.5 and the pilot piston 3 fixedly connected thereto may be positioned exactly only by changing the magnetic force.
The control movement of the pilot piston 3 required for the positioning of the piston rod of a large working cylinder can be performed ideally using the directional control valve implemented according to the invention. A position measurement of the actuating piston 1.5 and/or the pilot piston 3 is not necessary. A position measuring system in or on the directional control valve, which is sensitive to heat and susceptible to failure, can therefore be dispensed with. A position measuring system is advantageously only provided on the working cylinder.

Claims

1. A directional control valve for controlling working cylinders or servomotors, in particular an actuating cylinder of a turbo-machine such as gas and steam turbines;

1.1 having a force-regulated magnet (1.9) and

1.2 having a hydraulic unit, comprising a control housing (2), in which a pilot piston (3) is situated so it is displaceable in the axial direction of the directional control valve,

1.3 the control housing (2) having at least three hydraulic connections, namely a first pressure connection (P) for the connection to a hydraulic pressure supply, a consumer connection (A, B) for the connection to the working cylinder or servomotor, and a tank connection (T) for the connection to a hydraulic tank; and

1.4 the flow cross-section between the hydraulic connections (A, B, P, T) being variable by displacement of the pilot piston (3);

characterized in that

1.5 an additional actuating unit (1) is provided, which comprises the force-regulated magnet (1.9) and an additional control piston (1.1), which is displaceable in the control housing (2) or in a flange (1.2) attached on the control housing (2), and which is displaceable using a force-regulated magnet (1.9) and which varies the flow cross-section between an actuating unit pressure connection (p), an actuating piston connection (a), and an actuating unit tank connection (t) by displacement;

1.6 the actuating unit (1) also comprising an actuating piston (1.5), which is also non-positively and/or positively connected on the pilot piston (3) so it is displaceable in the axial direction of the directional control valve, and divides a piston room (1.10) into two piston room chambers (1.11, 1.12) which are sealed to one another, of which the first chamber (1.11) is hydraulically connected to the actuating piston connection (a), and

1.7 the actuating piston (1.5) being connected via a first elastic element, which acts against the hydraulic pressure force in the first piston room chamber (1.11), to the control piston (1.1) or being supported thereon, and being connected via a second elastic element, which acts against the hydraulic pressure force in the first piston room chamber (1.11), to the control housing (2) or the flange (1.2) or being supported thereon.

2. The directional control valve according to claim 1, characterized in that the first elastic element is implemented as a pressure element, in particular as a compression spring (measuring spring 1.4), which is positioned in the second piston room chamber (1.12), and/or the second elastic element is implemented as a pressure element, in particular as a compression spring (restoring spring 1.6), which is positioned in the second piston room chamber (1.12).

3. The directional control valve according to claim 2, characterized in that the first elastic element, in particular the measuring spring (1.4), has a different, in particular lesser spring force than the second elastic element, in particular the restoring spring (1.6).

4. The directional control valve according to one of claim 2 or 3, characterized in that the measuring spring (1.4) has a smaller diameter than the restoring spring (1.6) and is enclosed in the peripheral direction on its outer side by the restoring spring (1.6).

5. The directional control valve according to one of claims 1 through 4, characterized in that the control piston (1.1) is also displaceable in the axial direction of the directional control valve, and the pilot piston (3), the control piston (1.1), and the actuating piston (1.5) are situated concentrically one behind another and aligned with one another in particular in the axial direction.

6. The directional control valve according to one of claims 1 through 5, characterized in that the directional control valve is free of a position measuring device, which measures the position of one of the pistons (3, 1.1, 1.5) or of components connected thereto.

7. The directional control valve according to one of claims 1 through 6, characterized in that the control piston (1.1) is situated so it can slide in a cylindrical hole of the flange (1.2).

8. The directional control valve according to one of claims 1 through 7, characterized in that the actuating piston (1.5) is situated so it can slide inside a cylinder (1.7), which is inserted into the control housing (2) and/or in the flange (1.2) or is implemented in one piece therewith, and which delimits the two piston room chambers (1.11, 1.12) in the peripheral direction and/or on one side or both sides in the axial direction, and in particular the hydraulic connection between the actuating piston connection (a) and the first piston room chamber (1.11) is implemented in the cylinder (1.7) in the form of one or more holes (1.13).

9. The directional control valve according to one of claims 1 through 8, characterized in that the actuating unit pressure connection (p) is sealed hydraulically and pressure-tight with respect to the pressure connection (P).

10. The directional control valve according to one of claims 1 through 9, characterized in that a conductor is situated in the magnetic field of the force-regulated magnet (1.9), which is implemented as an electromagnet for an electrical activation, which is connected to the magnet (1.9) in such a matter that the magnetic force and thus the position of the control piston (1.1), the actuating piston (1.5), and the pilot piston (3) are regulated via the Hall voltage generated in the conductor.

11. An actuator, comprising a working cylinder, in particular the form of an actuating cylinder of a turbo-machine, and a directional control valve, which is connected to the working cylinder via hydraulic lines for controlling or regulating the position of an extendable and retractable piston of the working cylinder, characterized in that the directional control valve is implemented according to one of claims 1 through 10.

12. The actuator according to claim 11, characterized in that a position measuring device is connected to the working cylinder, which acquires the position and/or the covered distance of the piston of the working cylinder, and a control unit is provided, which regulates the force-regulated magnet (1.9) as a function of the measurement results, in particular in the form of an electrical voltage, of the position measuring device.